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Research News 2018

FBH has developed an InP MMIC process in which epitaxial layers are transferred from comparably fragile InP wafers to robust Si host wafers. Implementing through-silicon vias and wafer thinning are straightforward parts of the procedure, this process is now available as standard module to suppress substrate modes at highest frequencies.

Recently, FBH has presented the first GaN-based digital sequential power amplifier module that allows to flexibly tune the efficiency over a wide output power range (6 … 12 dB) while maintaining a small form factor and a large bandwidth.

At IMS in Philadelphia and the co-located ARFTG – Microwave Measurement Conference, the FBH presented papers showing future directions towards more agile telecom systems, operating at much larger instantaneous bandwidth and at a more limited power budget.

Power switching transistors are used in switch mode power supplies for power conversion - most of them carry current and have to block voltage in only one direction. GaN transistors from the FBH can be operated in both directions and thus enable particularly efficient T-type converters.

The FBH develops sophisticated tunable diode lasers based on a MOPA concept, e.g. for frequency conversion applications. It has identified the most effective mounting and assembling process to couple the seed laser light efficiently over several lenses into the amplifier chip.

The Chalmers model is one of the frequently used and well-known GaN HEMT models, featuring two implementations of capacitive effects: the capitance and the charge-based model. To achieve more precise results, both model parameters have been thoroughly analyzed.

Ps pulsed laser sources emitting in the yellow spectral range are requested for applications in life sciences. The FBH has developed very compact diode laser modules, including a 560 nm module with high peak pulse powers - at least a factor of 10 better compared to existing systems.

Such amplifiers are fundamental blocks of high-speed optical drivers, modulators, transceivers, and measurement systems. FBH has developed a stable amplifier with high linearity and low deviation from linear phase over a large bandwidth from DC to 95 GHz.

(In)AlGaN-based UV-B LEDs are promising candidates to replace established UV light sources in various applications. However, high defect densities in these materials, among others, limit their efficiency. The FBH has therefore studied the influence of EBL doping and EBL material composition on the emission power of 310 nm LEDs.

The FBH develops highly sensitive, fast-response and broadband THz detectors for CW and pulsed operation. Since fast THz cameras with high sensitivity are mandatory for many industrial applications, FBH is also working on focal plane arrays of THz detectors to transfer the excellent single detector performance to a THz camera.

Spaceborne quantum optical sensors for high-precision measurements rely on compact and robust narrow linewidth laser systems. The radiation hardness of the VHBGs which enhance the frequency stability of the employed laser modules was shown by FBH for typical low-earth-orbit conditions.

Improvements regarding the lateral beam quality of GaAs-based BA diode lasers strongly depend on the lateral temperature profile within the laser chip. FBH has recently made progress in understanding the effects regulating this profile.

Microwave plasmas can be used for a variety of applications. Accurate knowledge of their electrical behavior is indispensable to achieve high power output and efficiency. The FBH has developed a measuring method for precise characterization and a novel non-linear plasma model.

FBH presents broad area laser diodes reaching pulse powers of tens of watts and pulse lengths in the 10 ns range. These lasers are specially designed for Light Detection and Ranging (LiDAR) systems used in autonomous driving and for object detection.